A liquid cooling unit is well known as disclosed in the Japanese Patent Application Laid-open No. 2004-139187, for example. The liquid cooling unit employs a centrifugal or a vortex pump operating based on the rotation of a rotor.
Patent Publication 1:
JP Patent Application Laid-open No. 5-340375
Patent Publication 2:
JP Patent Application Laid-open No. 2004-139187
A piston pump employing a piston and a piezoelectric pump employing a piezoelectric element are well known. The piston and piezoelectric pumps enables an efficient circulation of coolant as compared with the centrifugal and vortex pumps. On the other hand, a large pulsation is generated in the piston and piezoelectric pumps. If an elastic tube or tubes such as a rubber tube or tubes are connected to the piston and piezoelectric pumps, the pulsation causes vibration of the tube or tubes. In the case of a notebook personal computer, for example, the vibration of the tube or tubes is transferred to the hands of a user through a palm rest. The user feels uncomfortable with the notebook personal computer. A rigid piping can be employed so as to avoid the vibration resulting from the pulsation. However, the rigid piping requires a high accuracy in positioning the components of the liquid cooling unit. This leads to a troublesome assembling operation and a higher production cost.